Cam body hoist



Nov. 18, 1958 w. J. WITWER 2,860,915

CAM BODY HOIST Filed March 11, 1955 4 Sheets-Sheet 2 v 20 20 INVENTOR.

WALLACE J. W/TWER wkm A TTORNE Y-S FIG. 2 B

W. J. WITWER Nov. 18, 1958 CAM BODY HOIST 4 Sheets-Sheet 3 Filed March 11, 1955 INVENTOR.

W/TWER WALLACE A TTORNE Y8 Nov. 18, 1958 w. J. WlTWER CAM BODY HOIST Filed March 11, 1955 4 Sheets-Sheet 4 INVENTOR. WALLACE J. W/TWE'R QA kW A TTORNE Y5 United States Patent 2,860,915 CAM BODY HOIST Wallace J. Witwer, Gallon, Ohio, assignor to The Cobey Corporation, Galion, Ohio, a corporation of Ohio Application March 11, 1955, Serial No. 493,619 10 Claims. (Cl. 298-22) This invention relates to body hoists, and more particularly to hydraulically-actuated body hoists of the type customarily employed on dump trucks and the like.

It is a primary object of my invention to provide a hydraulic hoist of the character described which shall contribute increased stability to the body at elevated positions.

Another object of my invention is to provide a hydraulic hoist having improved directional thrust characteristics in relation to its supporting structure.

A further object of my invention is to provide a hydraulic hoist of extremely compact form which will re quire a smaller and lighter supporting structure than the prior art devices.

Other objects and advantages of my invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same,

Fig. l is a fragmentary front elevation of a hydraulic hoist embodying the features of my invention, and showing the hoist in an elevated position.

Fig. 2 is a view similar to Fig. l but showing the hoist in lowered position.

Fig. 3 is a view in elevation as seen from the left side of Fig. 2.

Fig. 4 is a view similar to Fig. 3 but showing the hoist in elevated position.

Fig. 5 is a detail view of .the roller arrangement, taken on line 5--5 of Fig. 4.

Fig. 6 is a fragmentary top plan view similar to Fig. 5 but showing a modified form of roller arrangement.

Fig. 7 is a longitudinal cross-sectional view taken on line 77 of Fig. 6.

Fig. 8 is a transverse cross-sectional view taken on line 88 of Fig. 6.

Fig. 9 is a view similar to Fig. 1, but showing a modified hydraulic cylinder arrangement.

Fig. 10 is a fragmentary cross-sectional view taken on line 1010 of Fig. 9, but showing the hoist in lowermost position.

Referring more particularly to Figs. 1-5 of thedraw ings, I have shown an auxiliary frame or supporting structure 10 for the hoist, to the rear end 11 of which may be pivotally secured any suitable body structure 12. The sub-frame 10 is secured over the frame (not shown) of the truck in a manner well known in the a-rt..

The sub-frame 10 includes a pair of side rails 13, which may be of angle iron or the like, and to which are rotatablysecured the transverse tubular cross-members or hinge members 14 and 15, as by means of collars 16.

The forward cross-member or shaft 14 is free to rotate axially, and has a cam element 17 pivotally secured to each end thereof, as by pivot pin 18, for initial movement in a substantially vertical plane, as shown in Fig. 2. The plate cams 17 may be fabricated as weldments consisting of spaced parallel body elements 19 and a peripheral band or surface.20 which provides the camming surface. The cam surface 20 is engageable with a roller. 21 which is rotatably secured in the spaced elements 22 forming a cross-member 23 of the body frame 12; The body structure 12 also includes side rails 24 which underlie and are secured to the cargo body 25. The

. alignment.

rear end of each of the rails 24 is provided with a dependent arm 26 which is secured to the rear cross-member 15 of the sub-frame 10.

Means for actuating the cams 17 is provided in the form of a fluid motor 27 including the independent hydraulic cylinders 28 which are assembled in longitudinal The rods or rams 29 of the fluid motor are each pivotally secured to one of the cams 17, as by pivot pin 30. As best seen in'Fig. 2, the pin 30 is spaced laterally from the pivot pin 18 and is positioned or located above the axis of member 14 or the imaginary line connecting the pins 18, when the cams 17 are in their lowermost position. Thus, a short lever'arm is created between pin 18 and pin 30 which increases in length as the earns 17 rotate outwardly and progressively elevate the pins 30.

The cam surface 20 is designed to present a progressively increasing radius of curvature as it is rotated from its inoperative position (Fig. 2) to its fully elevated position (Fig. 1). By correlating the cam design with the variable lever arm, a uniform thrust or force characteristic can be maintained throughout the hoisting cycle.

Hydraulic fluid under pressure is supplied to the fluid motor 27 by any suitable means through the conventional hoses 31 and fittings 32.

'It will be noted that the anti-friction rollers 21 are somewhat spherical in form so that the cam surface 20 may maintain a tangential relationship to the roller even though the cams 17 do not maintain a position normal to the body structure 12 as the cams are elevated.

It willv be understood that in operating the hydraulic hoist a uniform hydraulic fluid pressure is applied to both cylinders 28. to cause displacement of the rams 29. The rams 29 project in opposite directions and act upon the cams 17 to rotate them outwardly from the position shown in Fig. 2 to the position shown in Fig. l, or any position intermediate thereto. The rotation of the cams causes cam surface 20 to act upon anti-friction rollers 21 and thuselevate the body 12 so that it pivots about the axis of the cross-member 15 which is journalled in side rails 13 of the sub-frame 10.

As the cams 17 rotate, the fluid motor27, which is otherwise unsecured, floats or rises with the movement of the cams and inherently equa-lizes or synchronizes the movement of the cams. thrust of the rams 29 is transverse of the frame 10 and the cams 17 act as reaction members, there is no concentrated reaction thrust on the frame 10, as in the straight-line typeof prior art hydraulic hoist units, and consequently the'entire frame structure can be lighter and smaller. Furthermore, it will be noted, that the initial direction of force which is applied to the body 12 by the cams 17 is vertically upward or normal to the body '12. This minimizes the thrust on the rotatable placed upon such hinge members by the almost horizontal thrust initially applied by the prior art devices. The avoidance of such a major horizontal force vector in my'device makes it unnecessary to employ a heavily reinforcedframe structure and hinge structure, and thus permits a further lightening of the frame structure without any sacrificeof necessary strength.

In addition to the improved thrust characteristics above described, the disclosed hoist structure embodies the characteristic of stability at elevated positions. It will be apparent that as the body 12 is raised and tilted, the camsmove outwardly to provide a stable two-point support for the body at widely spaced points. There is therefore no tendency for the body to twist or bend, as in the case where the hoist mechanism engages the body medianly thereof. The stability feature is enhanced by the fact that the disclosed hoist structure can occupy Inasmuch as the reaction a position much closer to the pivotal axis of the body 12 than can the prior art devices, and therefore the effective length or projection of the cam 17 need be correspondingly less than that of prior art devices to effect a selected degree of inclination of body 12.

In Figs. 6-8, I have shown a modified form of body frame structure in which the cross-member 23 of the body frame 12 is provided with stub shafts 33 which are journalled in bearing blocks 34 in the side rails 24. The cross-member 23 is therefore rotatable axially instead of being rigidly secured to the side rails 24, as in the first-described form of invention.

The cross-member 23' carries rotatable cylindrical antifriction rollers 35 which are each engaged by the cam surface of acam 17.

As best seen in Fig. 8, the cross-member 23 may be of semi-circular cross section with parallel wall extensions 36 which terminate in inwardly extending flanges or fingers 37. The fingers 37 underlie the cam surface band 20 and serve to prevent the body 12 from disengagement with the cams 17 Inasmuch as cross-member 23' is rotatable, it will rotate in response to the changing angularity of the cams 17 as the body 12 is elevated, and thus the rollers will retain a position normal to the band 20 and will remain in full face-to-face engagement with the cam surface 20 throughout the hoisting cycle. This arrangement prevents any longitudinal shifting movement of the cam 17 relatively to the cross-member 23'.

In Figs. 9 and 10, I have shown a modified form of the invention which is especially suited for conditions where it is necessary or desirable to provide for greater initial force or thrust at the start of the hoisting cycle, than can be obtained in the previously described form of invention.

In this embodiment, the forward hinge member or shaft 14' is in the form of a crankshaft having an axially offset portion 38 which is equidistant from the ends of the shaft. The offset 38 serves as the support or reaction member for two hydraulic cylinder units 39 each of which is pivotally secured to a pivot pin assembly 40 which is rigidly secured to the offset 38.

The cylinder units 39 extend between the body elements 19 of the plate cams 17, and the ram 41 of each cylinder unit is pivotally secured to a pivot pin 42 intermediate the elements 19 of one of the cams.

As best seen in Fig. 10, when the cams are in inoperative position, the shaft 14' is in a plane which is at a slight angle to the vertical. This permits the cylinder units 39 to be mounted in vertical alignment with the plane of the cams 17, while at the same time enabling the pivot assembly 40 to be located directly on top of offset 38 so that maximum support for the cylinders 39 is provided. It will also be noted that the pivot pin connection 42, which is intermediate the cam elements 19, minimizes the shearing stresses which are inherent in the cantilever type of connection provided by the previously described pivot connection 30.

The cylinders 39 are oppositely disposed at an acute angle to the horizontal axis of shaft 14', as for example 30-45, so that the initial thrust of the rams 41 has a sizable vertical force component. The angularity of the rams 41 also provides a force-compounding lever arm (between pins 18 and 42) which, due to the physical characteristics of the arrangement, is at a maximum at the start of the hoisting cycle. Consequently, the cylinder units 39 may be relatively of smaller size than the previously described cylinder units 38, as maximum load conditions and maximum cylinder thrust both occur at the start of the hoisting cycle.

Preferably, a volume equalizer 43 is connected in the fluid supply system so that both cylinder units 39 will be provided with equal volumes of the hydraulic fluid and movement of the cams 17 will therefore be synchronized.

It is to be understood that the forms of my invention, herewith shown and described, are to be taken as preferred examples of the same, and that various changes in the shape, size and arrangement of parts may be resorted to, without departing from the spirit of my invention, or the scope of the subjoined claims.

Having thus described my invention, Iclaim:

1. In a truck body hoist, the combination of a frame, a pair of plate cams pivotally secured to said frame for rotation in a substantially vertical plane transverse of the body, each of said cams having a progressively increasing radius of curvature, and means for simultaneously rotating each of said plate cams into body elevating engagement with the body.

2. In a truck body hoist, the combination of a frame, a pair of plate cams pivotally secured to said frame and having peripheral portions successively operatively engageable with the truck body, and opposed fluid-actuated rams connected to said cams for effecting simultaneous rotation thereof to body-elevating position.

3. In a truck body hoist, the combination of a frame, a pair of plate cams pivotally secured to said frame and operatively engageable with the truck body, and opposed fluid-actuated rams extending transversely of the body and connected to said cams for effecting rotation thereof into body-elevating position.

4. In a truck body hoist, the combination of a frame, a pair of cams pivotally secured to said frame and operatively engageable with the truck body, and fluid-actuated means supported by said pair of cams for effecting opposing body-elevating rotation of said cams.

5. In a truck body hoist, the combination of a frame, a shaft secured transversely of said frame for axial rotation therein, a pair of cam elements pivotally secured to said shaft for rotation about an axis normal to the axis of said shaft and operatively engageable with the truck body, each of said cams having body-engaging portions of progressively increasing curvature, and means for rotating said cams into body-elevating position.

6. In a truck body hoist, the combination of a frame, a shaft secured transversely of said frame for axial rotation therein, a pair of plate cams having a progressively increasing radius of curvature pivotally secured to said shaft for rotation about an axis normal to the axis of said shaft and operatively engageable with the truck body, and cam-actuating means associated with said shaft for bodily movement therewith.

7. A combination as defined in claim 6, wherein said means comprise a fluid motor.

8. A combination, as defined in claim 6, wherein said means comprises a fluid-actuated ram extending transversely of said frame and engaging said cams.

9. In a truck body hoist, the combination of a frame, a shaft secured transversely of said frame for axial rotation therein, a pair of cam elements pivotally secured to said shaft for rotation about an axis normal to the axis of said shaft and operatively engageable with the truck body, fluid-actuated motors operatively engaging said earns to effect body-elevating rotation thereof, and means connecting said fluid motors to said shaft for rotary movement therewith.

10. A combination, as defined in claim 9, wherein said shaft is provided with a crank arm and said means comprises a pivot connector pin secured to said crank arm.

References Cited in the file of this patent UNITED STATES PATENTS 1,260,560 Longenecker Mar. 26, 1918 1,394,113 Page Oct. 18, 1921 1,428,293 McEldoWney Sept. 5, 1922 2,452,516 Brick Oct. 26, 1948 2,467,056 Schmidtke Apr. 12, 1949 2,470,360 Messick May 17, 1949 2,721,097 Rittenhouse Oct. 18, 1955 

